Predictive Residual Ovality for Reel-Laid Pipelines in Deepwater

Abstract

Accurate determination of residual ovality is an important parameter for a successful deployment of single pipeline and pipe-in-pipe in deep waters wherein the integrity of empty pipes during installation depends upon the collapse resistance under external hydrostatic pressure. The reel-lay process of installation during which pipeline undergoes multiple strain cycles due to spooling, reeling and straightening has a significant bearing on pipe ovalisation and hence accurate determination residual ovality at the end of straightening process is one of the key inputs. It is industry practice to use numerical finite element analysis techniques to predict residual ovality of pipelines as full scale testing is expensive and time consuming. In view of the importance of residual ovality on the pipeline integrity particularly for deepwater applications, an integrated approach of testing and finite element simulation have been used to identify the correct numerical model that predicts residual ovality accurately. This paper discusses the full scale tests performed which include material testing and bend tests performed to simulate spooling and straightening process and the pipeline deformations recorded using laser measurements at different cycles of bending process. The paper presents a brief summary of numerical finite element analyses performed to validate the test results and the effect of element types and material models used in the finite element analyses on the predictability of residual ovality. The material evolution models and their effect on the predictability of remaining ovality are discussed in the paper. Comparisons are made on the predictive residual ovality for reel lay process on single pipe and pipe-in-pipe. The effect of residual ovality on the pipeline integrity for the lateral buckling limit state under combined bending and external pressure are discussed in the paper.

Research on Dynamic Response of Pipeline under the Reeling Process and Laying Process

“…Ovalization reduces the bending stiffness of the pipe and leads to instability of limit loads, and deformation in the circumferential direction leads to circumferential compression and tension. The non-uniform strain distribution within the pipe segment along the circumferential axis governs the extent of ovality [4]. Although some degree of recovery occurs when the pipe is unwound from the reel, a degree of permanent ellipticity persists, exerting a noteworthy impact on the pipe's performance.…”

“…2023, 11, x FOR PEER REVIEW 2 of 22 compression and tension. The non-uniform strain distribution within the pipe segment along the circumferential axis governs the extent of ovality [4]. Although some degree of recovery occurs when the pipe is unwound from the reel, a degree of permanent ellipticity persists, exerting a noteworthy impact on the pipe's performance.…”

Numerical Simulations and Experimental Study on the Reeling Process of Submarine Pipeline by R-Lay Method

“…As an important feature of pipe-bending response, ovalization has been taken as a research object by many scholars. Braize [7] studied the relationship between ovalization As the deformation of the pipeline gradually changes from an elastic to plastic state, permanent deformation of the pipeline will cause the cross-section shape of the pipeline to gradually change from round to ellipse; this phenomenon is called ovalization [6]. For pipes used in the reel-lay method, at the 6 o'clock and 12 o'clock positions of the neutral axis, the deformation of the pipe cross-section in the circumferential direction will cause circumferential compression and stretching.…”

Finite Element Analysis of Cyclically-Loaded Steel Pipes During Deep Water Reeling Installation

“…In particular, the pipe experiences large strains when it is spooled onto the reel, often in the sea surface sea bed (1): reeling (2): unreeling (3): ramp bending (4): straightening (5): unloading range of 2%, which requires that the pipe is mechanically straightened out before its installation. The five consecutive steps of reeling process are show in Fig.…”